Pump apparatus



J. T. MARSHALL ET AL ,781,727

PUMP APPARATUS Feb. 19, 1957 Filed March 15, 1950 3 Sheets-Sheet 1 C L.UTCH/NG MW To FUEL SuPPLY 1N VEN TORJ CHARLES 0. WE/JENBACH JOHN 7? MAEJHALL M s a /W ATTORNEY 3 Sheets-Sheet 2 PUMP APPARATUS J. T. MARSHALL ETAL a, i mw V 4 L l s l 3 m Q R ww ww H mm Q. 427 \\Q a w% \v w\ Feb. 19, 1957 Filed March 15, 1950 Y mm. w m E B 0 EN T WEE T 5 A CM wm w [MM B m 1957 J. "r. MARSHALL ETAL 2,781,727

PUMP APPARATUS Filed March is, 1950 3 Sheets-Sheet 3 ssaszQm NwQvnN \Emm soot k TAA E WWW w WEE T 1MA A M .7 ON 5% U m O w n v n m N a a -95 zanprsa United States Patent PUMP APPARATUS John T. Marshall and Charles 0. Weisenbach, South Bend, Ind., assignors to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application March 15, 1950, Serial No. 149,742

2 Claims. (Cl. 10311) This invention relates to apparatus for pressurizing fuel for use in engines.

It is a principal object of this invention to provide a device capable of supplying fuel under pressure to an engine over a wide operating range from start to maximum speed.

An important object of the invention is to provide a fuel pressurizing apparatus characterized by its absence of reciprocating parts and ability to increase the pressure of the fuel in proportion to the speed of an associated driving device.

Another very important object of the invention resides in the provision of a fuel pressurizing apparatus characten'zed by its absence of a by-pass and ability to discharge only the quantity of fuel that will flow for a given pressure.

A still further important object of the invention resides in the provision of a pressurizing apparatus comprising a first pump capable of putting fuel under pressure to be supplied to an engine during the starting period, a second pump capable of putting fuel under pressure after the engine has acquired a predetermined speed, and means controlled by the pressure developed from said second pump for rendering said first pump ineffective.

The above and other objects and features of the invention will be apparent from the following description of the apparatus taken in connection with the accompanying drawings which form a part of this specification, and in which:

Figure l is a schematic representation of the pressurizing apparatus of the invention associated with a jet engine;

Figure 2 is a view in section through the clutch mechanism and gear pump; and

Figure 3 is a graphical representation of pressure versus pump R. P. M. and flow.

Although the pressurizi-ng system of the invention is hereinafter exemplified in connection with a jet engine the device has other applications.

Referring now to Figure l, the reference numeral 12 designates a nacelle in which a jet engine 14 is mounted. The engine is equipped with a rotatable driving shaft 18, to which is connected the apparatus of the invention, in a manner to be hereinafter described. Fuel for the engine is received from a source, not shown, via conduit 19, pressurized by our invention, and delivered through the pipe line 20 to the manifold 21, from whence the fuel is distributed to burners 22.

The pressurizing apparatus comprises a multi-stage centrifugal pump 24, drivably connected to the engine shaft 18, which shaft also drives a gear pump 26, through an automatic clutching mechanism 28. I

The fuel supply conduit 19 has one end connected to the fuel source, not shown, and its other end connected to the branch lines 30 and 32, which line communicate with the inlet side of the pumps 24 and 26 respectively. Branch lines 34 and 36 connect the discharge side of the pumps 24 and 26 respectively, to the common pipe line Patented Feb. 19, 1957 20,- which carries the pressurized fuel to the manifold 21. Check valves 38 and 40 are located at the junctions of branch lines 34 and 36 with the pipe line 20. It is a function of these valves to allow fuel to flow in one direction only, namely, from the pump outlets to the pipe line 24) but prevent flow in the opposite direction or from the discharge side of one pump through the other pump in reverse direction. During the change-over from one pump to the other both valves are open, since the pumps are concurrently contributing to the flow at this time.

Since it is a purpose of this invention to furnish a gear pump for delivering fuel to the engine during the starting period and a centrifugal pump for supplying fuel after that time, means has been provided for rendering the gear pump ineffective as a fuel supplying device after the centrifugal pump has taken over. This means i in the form of an automatic clutching mechanism 28 interposed between the drive shaft 18 and the gear pump 26. The clutching mechanism is made responsive to the centrifugal pump discharge pressure by connecting one end of a pipe line 42 to the branch line 34, and the other end of the line to :the clutching mechanism 28. When the pressure in the line 34 attains a predetermined value the gear pump is disconnected or declutched from the drive shaft 18. During the changing over period from one pump to the other, the pumps are simultaneously discharging fuel into the common line 20.

The details of the clutching mechanism and the gear pump are best illustrated in Figure 2. In the present emhodiment the pumps and clutching mechanism are contained in an integrated or main housing 44, comprised of the sections 46, 48, and 50 in which the centrifugal pump 24, fluid drive 52, and gear pump 26 respectively are housed. These sections are retained in assembled relationship by bolts 54, 56 and 58. The centrifugal pump i drivably connected to the shaft 18, which is suitably supported in the housing. The fluid drive 52 is provided with an impeller wheel 60, securely fastened to one end of the drive shaft 18, and a turbine wheel 61 fixed to an internally splined hollow shaft 64 suitably carried by a bearing 66. The turbine wheel comprises two sections 62 and 63, the former of which is equipped with a circular plate 68, having a flange portion 69, which registers with a flange 70 of the section 63. Bolts 71 hold these sections 62 and 63 in abutting relationship. The circular plate 68 is formed with an axially extending cylindrical portion 72 supported by a bearing 73. The circular plate 68 together with the section 63 form a shroud for the fluid drive 52. Restricted passages '74- in the turbine wheel allow fluid to escape from the fluid drive. The hollow shaft 64 is formed with a gear 75, which meshes with a gear 76, secured to the end of a stub shaft 78, splined to a shaft integral with one of the gears 82 of the gear pump 26. The gear pump is thus drivably connected to the shaft 13 through the fluid drive 52.

The gear pump is directly connected to the drive shaft 18 via cone clutch 84, and externally :splined shaft 86, slidably disposed in the hollow shaft 64. The end of the externally splined shaft 86, opposite the cone clutch, is equipped with a piston 88, slidably positioned within a cylinder 90. A bearing 92 is interposed between one end of the shaft 86 and the piston 38 for carrying that end of the shaft. The arrangement of the bearing 92 on the shaft and in the piston is such that axial displacement of the piston slides the shaft, but rotation of the cone clutch does not rotate the piston. The pipe line or passage 42 communicates the discharge side of the centrifugal pump with the left end of the cylinder fit. A spring 94 is interposed between the right end of the cylinder and the piston 88 to thereby urge the latter to ward the left end of the cylinder. It will be noted that this spring eifects engagement of the cone clutch 84.

Fluid under pressure for the fluid drive 52 is obtained from the engine oil supply, not shown. The fluid for the fluid drive could be taken from the fuel supply, not shown. Oil is delivered under pressure from the engine oil supply, not shown, to the cylinder 90, through a passage 96, which terminates in the side wall of the cylinder to the right of the piston 33, when in the position shown in Figure 2. A longitudinal passage 98, in the splined shaft 86, connects the right end of the cylinder 90 with the fluid drive. Oil is discharged from the fluid drive through passages 74, whence it is returned to the engine oil supply by means, not shown. This arrangement permits continuous circulation of oil through the fluid drive so long as the passage 96 is uncovered by the piston 88.

Figure 3, shows a graph of the pressures and flows developed by the two pumps under varying conditions of engine or pump R. l. M. It is obvious from the curve sheet that a centrifugal pump designed for given maximum engine requirements would not be adequate for supplying fuel during the engine starting period where the starting pressure requirements are around 200 p. s. i. at 500 R. P. M. for example, because of the low pressure and low fuel delivery.

lt will be noted that for any constant speed, the pressure rises as the flow is decreased. For example, at 12,000 R. P. M. the flow of fuei is approximately 12,000 lbs. per hour at a pressure of 1.165 p. s. i., while at zero fuel flow the pressure is 1,400 p. s. i. This characteristic is very important in jet engine supply pumps, since the quantity of fuel used at higher altitudes is much less than that at sea level.

Operation of the apparatus is as follows:

with the prcssurizing apparatus at rest the various parts will assume the positions shown in Figure 2, wherein the gear pump is connected to the shaft 18 via the clutch mechanism S 5. CranlLing the engine rotates the shaft 13 which drives the gear pump for forcing fuel into the manifold 21, from whence the fuel is distributed to the burners 22. This cranking operation drives the gear pump at a speed which will establish sufficient fuel fiow for starting the engine, after which time the centrifugal pump output alone becomes adequate for furnishing fuel at the required rate.

When the centrifugal pump discharge pressure reaches a predetermined value the piston 88 is moved to the right. thereby disengaging the cone clutch 84 and covering the passage 96, the latter action cutting off the supply of engine oil to the fluid drive. Continued rotation of the fluid drive soon discharges the remaining engine oil through the passages 74, to render the fluid drive inoperativc. The gear pump is now ineffective as a fuel pressurizing device; the entire fuel demand is handled by the centrifugal pump.

When the engine is shut down the centrifugal pump discharge pressure gradually falls below the predetermined value required for moving the piston 88 to the right, thus allowing movement of the piston to the left under the influence of the spring 94, uncovering the passage 96. Communication is again established between the fluid drive and the engine oil supply, thus enabling fluid drive to once again function as a driving medium for the gear pump. A further reduction in engine or drive shaft speed, hence a further reduction in the centrifugal pump discharge pressure, permits additional piston movement to the left and eventual engagement of the cone clutch. The establishment of a fluid drive connection to the gear pump before the engagement of the friction clutch reduces the shock load which would otherwise occur.

Although this invention has been described in connection with certain specific embodiments, the principles are susceptible of numerous other applications that will readily occur to persons skilled in the art.

Having thus described the various features of the invention, what we claim as new and desire to secure by Letters Patent is:

We claim:

1. An apparatus for pressurizing fluid comprising a gear pump provided with an inlet and an outlet, a centrifugal pump provided with an inlet and an outlet, 21 common source of fluid connected to the inlets of said pumps, a common discharge line connected to the outlets of said pumps, said pumps being provided with a common drive, a control mechanism interposed between the common drive and said gear pump, said mechanism including a fluid drive, a friction clutch, a conduit adapted to connect said fluid drive to a source of fluid, and means conscious to the centrifugal pump discharge pressure for disengaging said clutch at a predetermined pressure and cutting off the fluid to said drive at another higher pres sure.

2. An apparatus for pressurizing fluid comprising two pumps having common inlets and outlets, driving connections for said pumps, a mechanism in one of the connections for controlling one of the pumps, said mechanism including a mechanical drive and a fluid drive, a clutch in the mechanical drive, a fluid connection from the fluid drive to a fluid source, and means operatively connected to said clutch and responsive to predetermined pressures from the other pump for controlling the clutch and the fluid through said connection.

References Cited in the file of this patent UNITED STATES PATENTS 1,891,618 Campbell Dec. 20, 1932 1,982,711 Vickers Dec. 4, 1934 2,390,204 Curtis Dec. 4, 1945 2,464,144 McConaghy Mar. 8, 1949 2,607,297 Walker Aug. 19, 1952 FOREIGN PATENTS 663,396 Germany 1938 918,123 France 1946 

